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REVENUE - Provisional Copper and Gold Sales (Details)
ozt in Thousands, lb in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2017
USD ($)
lb
ozt
Dec. 31, 2016
USD ($)
lb
ozt
Copper    
Disclosure of Disaggregation of Revenue [Line Items]    
Volumes subject to final pricing Copper (millions) Gold (000s) | lb 40 44
Impact on net income before taxation of 10% movement in market price US$ $ 13 $ 11
Gold    
Disclosure of Disaggregation of Revenue [Line Items]    
Volumes subject to final pricing Copper (millions) Gold (000s) | ozt 0 13
Impact on net income before taxation of 10% movement in market price US$ $ 0 $ 2